This investigation is concerned with the analysis of polymorphic enzyme phenotypes in tumor and normal tissue samples derived from the same patients. We will analyze the isozyme phenotypes of 10 polymorphic enzyme systems in order to determine if the extensive loss of functional gene expression we have observed in cultured human tumor cells occurs in in vivo tumors and to determine to what extent it is affected by the growth of tumor cells in culture. Methods will include starch, polyacrylamide and cellulose acetate strip electrophoresis and isoelectric focusing in polyacrylamide gels. The reductions in levels of heterozygosity will be used to estimate the extent of the loss of functional gene expression occurring at each of the 10 polymorphic enzyme loci in the neoplastic tissue. Attempts will be made to relate the loss of functional gene expression to the level of differentiation of the tumor sample and to determine if some tumors are more prone to the loss of heterozygosity than others.